Electromagnetic radiation is a term used to describe a stream of energy-bearing particles that travels outward from an electromagnetic source. The energy in these streams can vary extensively in power, and is measured by the electromagnetic spectrum. Electromagnetic radiation can be beneficial, harmless or extremely dangerous to humans, depending on the source, level of radiation, and duration of exposure.

There are both natural and man-made sources of electromagnetic radiation. The sun, for instance, is an intense source of radiation that can have both positive and negative effects on living things. The sun also produces both visible and invisible electromagnetic streams. Ultraviolet rays from the sun are invisible and cause sunburn and skin cancer if overexposure occurs. A rainbow, however, is a visible and harmless part of the electromagnetic effect caused by the sun, as human eyes detect the visible wavelengths of light as different colors.

Man-made sources of electromagnetic radiation include X-rays, radio waves, and microwaves, although some natural sources exist as well. Microwaves and radio waves are used by humans to power machines and increase communication abilities. Cell phones, radios, microwave ovens, and and radar all create electromagnetic radiation. This has lead to some concern that the growing prevalence of electromagnetic devices will lead to large increases in illnesses caused by radiation, such as cancer. As of yet, few studies suggest that exposure to household devices is strong enough to cause genetic mutation or cancer.

Scientists break down electromagnetic radiation into two types, non-ionizing and ionizing. Non-ionizing varieties include visible radiation, infrared radiation, and most types of low-energy radiation like radio and microwaves. Overexposure to non-ionizing radiation can cause burns to the skin, but is unlikely to cause genetic mutation or alter cellular structure. Ionizing radiation, such as that used in cancer treatments, is made up of high-energy wavelengths and can actually alter or mutate DNA. While this can be used to treat cell-affecting diseases like cancer, it can also cause serious and possibly fatal cellular damage leading to birth defects or radiation sickness.

The power contained in electromagnetic radiation can be both helpful and destructive to humans. Although it has become a vital part of technology, it also remains an enormous liability to human health. Overexposure to radiation, whether in an acute dose or a slow, continual intake, can quickly lead to illness and even a painful death. However, as electromagnetic radiation is also a natural part of the human environment, exposure to some radiation is unavoidable.

Since the first discoveries about radiation in the mid-19th century, humans have been fascinated by the delicate balance of risk and reward implicit in its use. While exposure is impossible to avoid, technology as simple as sunscreen or as complicated as radiation shields requires constant research and discovery in order to minimize human risk. Improving safety, preventing harm, and finding new uses for electromagnetic radiation continues to be an important area of discovery and research in the modern scientific world.